There was a choice for Multiplication or Fixation between the two NPCs, but when the card was selected it showed up as a Dissolution card with the Salt effect. When I clicked on the character icon, it said that the Fixation card was selected, but it still had the Salt effect instead of the Mercury one.
Since another user observed a similar issue last night, I have been trying to recreate the event without success. If it occurs again, it would be a huge help if you could take a screenshot of the game and the affected player's description. I have made an adjustment to streamline things which may have the added effect of fixing this error. But if not, I think I will need more help finding the cause. Thanks for your help.